My first scientific paper, together with @raghuastro and @garreltm! :D We've derived new 21-cm constraints on fuzzy dark matter (FDM), an alternative to cold dark matter (CDM) that has gotten much attention as of late. (1/n)
(2/n) FDM suppresses structure formation on small scales, and the smallest structures form early in the Universe. Because of this, studying Cosmic Dawn offers us not just a glimpse of the first stars and galaxies, but also a glimpse of the nature of dark matter!
(3/n) 21-cm cosmology offers us a promising way of studying Cosmic Dawn by tracking the evolution of the neutral hydrogen in the early Universe, the state of which has a sensitive dependence on the nature and multitude of the first astrophysical sources of radiation.
(4/n) Earlier this year, Judd D. Bowman and collaborators presented the first claimed detection of the sky-averaged 21-cm signal from Cosmic Dawn. The timing of this signal would indicate the presence of stars a mere ~ 100 million years after the Big bang!
(5/n) This claimed detection used the EDGES *low-band* experiment. Soon thereafter, Adam Lidz & Lam Hui showed that FDM would fail in its original mission were the EDGES signal to be a genuine detection. The existence of stars this early is simply inconsistent with FDM.
(6/n) However, R. Hills et al. have raised concerns about the foreground modelling used by Bowman et al., and so there is some debate on whether the signal is genuine. In the mean time, before independent confirmation (e.g. by LEDA), this constraint on FDM is on shaky ground.
(7/n) Our paper has managed to derive constraints on FDM from the EDGES high-band experiment, which did not detect the signal that the low-band experiment did (it is focused on a different freq. range). Thus, our constraints does not hinge on the EDGES signal being genuine.
(8/n) The conservative constraint we derive on the FDM particle mass m_22 is m_22 > 6 (in case of inefficient or very efficient X-ray heating). For nominal X-ray heating, this is increased up to m_22 > 20. Lower particle masses produce too narrow absorption signals which is ...
(9/n) inconsistent with constraints from EDGES high-band. The original motivation of FDM was to explain ~ kpc sized constant-density cores in dwarf galaxies, and simultaneously suppress galaxy formation in halos with masses < 10^10 Solar masses. This requires m_22 ~ 1 - 3.
(10/n) m_22 > 6 would therefore imply the failure of FDM in living up to its original promise, and could be seen as additional evidence for CDM-like structure formation. As exotic and cool as FDM is, it doesn't seem to describe our Universe.
(11/n) References cited above:
Bowman et al: nature.com/articles/natur…
Lidz & Hui: arxiv.org/abs/1805.01253
Hills et al: arxiv.org/abs/1805.01421
Monsalve et al (EDGES high-band): arxiv.org/abs/1806.07774
Bowman et al: nature.com/articles/natur…
Lidz & Hui: arxiv.org/abs/1805.01253
Hills et al: arxiv.org/abs/1805.01421
Monsalve et al (EDGES high-band): arxiv.org/abs/1806.07774
